GlaxoSmithKline is close to ending a six-decade drought in relapse-preventing therapies for Plasmodium vivax—one of the most common forms of malaria—after its new drug tafenoquine cleared an FDA advisory committee.
The panel backed the efficacy of the tafenoquine regimen by 13 votes to zero, and its safety by 12 to one, in P. vivax-infected patients aged 16 or older, after the FDA published briefing documents (PDF) which backed the drug.
The drug’s long half-life in the body means that it can prevent relapse with one dose, unlike current therapy primaquine which needs a daily dose for two weeks, which was also the comparator arm in the main phase 3 trial supporting tafenoquine’s marketing application. That means it should be easier to deliver and improve compliance, particularly in countries with fewer healthcare resources.
GSK developed tafenoquine in partnership with Medicines for Malaria Venture (MMV) to address the need for a drug that can achieved a “radical cure” of this type of malaria—in other words, clear up the infection and prevent it from coming back. It has breakthrough status from the FDA for this indication.
The main endpoint of the trials was relapse-free efficacy six months after dosing, and overall the panel concluded that GSK and MMV’s drug performed as well as primaquine. There were some safety signals to take into account, including two cases of hypersensitivity. Patients prescribed the drug should also be tested for glucose-6-phosphatase dehydrogenase (G6PD) deficiency, as in these individuals it can cause severe anemia. That’s an issue that also affects parent drug primaquine.
P. vivax kills fewer people than the deadliest malaria parasite P. falciparum but is more widespread—affecting 16 million people in 2013, according to the World Health Organization—and can also cause severe disease and be life-threatening. It has a massive geographic range, with around half of P. vivax cases occurring outside Africa, and the WHO considers this species of the malaria parasite as the main barrier to its goal of eliminating malaria worldwide by 2030.
It’s been 12 years in development and if approved by the FDA will be the first new drug for this indication in 60 years, according to Pauline Williams M.D., GSK’s head of global health R&D, who also spearheaded the company’s development of a chlorhexidine gel product for the prevention of neonatal sepsis.
“Together with our partners, we look forward to the final decision by the FDA,” she said in a statement.
So far, the drug hasn’t been approved anywhere in the world, although it has been submitted for approval in Australia and a decision there is expected in the next few months. Approval in either the U.S. or Australia would help set up registrations in countries where P. vivax is endemic, and it would also open the door for WHO prequalification, which can accelerate uptake.